Method of making tubes



July 8, 1969 c. L- SPORCK AL METHOD OF MAKING Tuams Filed May 9. 1966 INVENTORS 06x04 M H M IM W/M H Avid W521i United States Patent US. Cl. 72-284 6 Claims ABSTRACT OF THE DISCLOSURE A method of making dimensionally accurate tubes comprising the steps of pushing a tubular blank into the throat of orbiting rollers to work the blank and cause the same to extrude away from the throat and as the blank just begins to extrude changing from the pushing force to a pulling force to cause the blank to continue to move through the roller throat.

This invention relates to metal working and in particular relates to methods for making tubes of a kind char acterized by precise dimensional accuracy.

The methods of the invention are particularly suitable for manufacture of tubes and cylinders for use in applications where dimensional accuracy such as wall thickness, diameter, and concentricity are of critical importance, Heretofore the manufacture of tubes of this nature necessitated extensive turning and/or grinding operations to obtain desired dimensional characteristics. The present invention provides a method for the manufacture of the kind of tubes and cylinders in question on a low-cost, highvolume basis.

In one aspect the invention contemplates a method for making tubes wherein a tubular blank is pushed into the throat of orbiting work rollers to cause the blank to extrude away from the throat, and as the blank begins to extrude, changing from the pushing force to a pulling force to cause the blank to move through the roller throat.

The pulling force is exerted on the extruding portion of the blank and brought into play in a manner to avoid any backforce on the blank of a magnitude or nature so that it will cause a dwell or slight stoppage of the rate of extrusion of the blank.

Thus in another aspect the invention contemplates a method for making tubes wherein a tubular blank is pushed into the throat of orbiting work rollers to cause the blank to extrude away from the throat, the rate of extrusion is measured, thereafter a means to exert a pulling force is moved at the measured rate of extrusion, and that force is then exerted on the extruding portion to pull the blank through the throat of the rollers. A pulling force is continued until the full length of the blank has been worked.

This concept of pushing a tube into the throat of the rollers to cause extrusion and then transferring over to a pulling force to continue the extrusion has several important advantages.

One of the most important advantages is that it enables the elimination of end loss. For example, in conventional mills where tubes are pulled, end loss is inevitable because the blank is inserted into the throat with part of the blank projecting outwardly. This free end is engaged by the means for exerting the pulling force and consequently this end is unworked and must be cut off after the tube is formed.

Another significant feature of this invention is that the pulling function is advantageously used to enhance the dimensional accuracy of the tubes. As noted heretofore, the

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invention provides that the tubes (except over a very small portion) is formed by pulling a blank through the throat of rollers. By utilizing this characteristic in conjunction with a gripping head which is moved along a predetermined and straight path, the concentricity of the tube is greatly enhanced.

Furthermore, the pulling feature enables one to advantageously correlate the dimensions of the rollers throat and the path of movement of the gripping head so that the wall thickness of the tube being formed is dimensionally stable; that is to say, it is of substantially the same thickness throughout the axial length of the blank, and this being true irrespective of the length of the blank pulled through the throat.

Another especially important feature of the invention is that tubes of considerable length, for example, thirty feet long, can be formed with the dimensional characteristics mentioned heretofore. This is especially important because it enables the manufacture of relatively sophisticated parts on a mass-production basis. For example, many applications for hydraulic cylinders specify cylinders of very close tolerance in concentricity and trueness of the bore. With the present invention long tubes can be formed and then cut to length for such applications, and the cut portions can be used without further machining. In those instances where additional machining is required the amount of material to be removed is held to an absolute minimum.

Furthermore the invention provides an additional advantage in that the rollers can be made to work on a highly finished mandrel head and thereby measurably enhance the surface finish both on the inside and outside of the tube.

The manner in which the invention is practiced will be apparent from the following description of drawings, wherein:

FIGURE 1 is a side elevation of one form of a machine which can be operated to practice the invention;

FIGURE 2 is a plan view of the machine of FIGURE 1.

In FIGURE 1 the machine includes a base 1 having a head stock section 2, left wing section .3, and right wing section 4. The head stock section 2 mounts a head stock 5 rotatably mounting a frame 6. The: frame 6 carries a plurality of reducing or working rollers 10. Preferably there are three rollers equally spaced about the axis A. The rollers are mounted in supports providing for radial adjustment with respect to the axis A as shown in Sporck Patent 3,245,243. As will be understood by those skilled in the art, this arrangement of the rollers forms a throat for the reception of a tubular blank B to be worked into a tube T.

On the left hand wing 3 is mounted a tail stock 11 which carries a mandrel feed mechanism 12. The mandrel feed mechanism mounts a blank feed means 13.

The mandrel feed 12 includes a jack 14 and a slide 15 which is connected to the stem 16 of the mandrel head 17. The jack 14 causes the slide 15 to move back and forth in a direction along the axis A. This motion causes the mandrel head 17 to move into and out of the throat of the rollers.

The axial position of the mandrel shown in the full lines is the normal inactive position. The mandrel is supported in this position by a roller 18 mounted on the piston and cylinder device 19. The piston and cylinder device 19 is adapted to controllably position the roller vertically.

The axial position of the mandrel head 17 indicated by the dot and dash lines 17a shows the position of the mandrel when it is within the throat of the rollers for the working operation. The mandrel supports the blank in the throat of the rollers so that the rollers work the Wall of the blank. The mandrel remains in the position as indicated by the dot and dash lines 17m during the working operation.

The blank feed means 13 comprises a pair of piston and cylinder devices 20 and 21 mounted on the mandrel feed mechanism 12. The pistons of the devices 20 and 21 are connected to a yoke 22 mounting a tube support 23. The end of a blank mounted on the mandrel is adapted to rest on this support. The devices 20 and 21 are adapted to move the yoke and support 23 to the right, and hence exert a pushing force to the blank mounted on the mandrel to cause the same to enter into the throat of the rollers.

For loading a tubular blank B on the mandrel the tail stock 11 is rotated about the axis C or until the mandrel assumes the position indicated by dotted line 17b in FIG- URE 2,. The tail stock 11 is power operated to rotate as described by the piston and cylinder device 24. The guideways 25 accommodate the rotational motion. After the tube is slipped on the mandrel, the tail stock and the mandrel are moved back to the position indicated in FIGURE 2 with one end of the tube resting on the support 23 and the other end of the tube resting on the mandrel head 17. It is pointed out that hydraulically operated locating pins (not shown) are adapted to be dropped into apertures to locate and hold the tail stock in the position shown in FIGURE 2.

The tail stock 11 also carries a pair of piston and cylinder devices 26 and 27 mounted on opposite sides of the axis A. The pistons of the device are adapted to engage a blank when the same is mounted on the support 23. The purpose of these devices is to steady the blank as it is pushed forward into the throat of the rollers by the yoke 22.

The left hand wing 3 also mounts blank support rollers 30 and 31, which function to properly support the blank as it is mounted on the mandrel head 17 and the support plate 23.

On the right hand wing 4 is a carriage 32 mounted for reciprocating motion left to right as viewed in FIGURE 2. The carriage is shown all the way to the right in its fully extendd position. The carriage mounts a gripper head 33 of conventional design. The gripper head is nonrotatable. When the carriage is moved all the way to the left of the gripper head is closely adjacent the throat of the rollers as is indicated by the dot and dash lines 33a. In this position the gripper head is adapted to receive the extruding end of the tube and engage the same for purposes of exerting a pulling force which is generated by virtue of the carriage being moved to the right.

The head stock section 2 mounts a tube support roller 34 which is adapted to be adjusted vertically by means of the piston and cylinder device 35. The right hand wing section 4 also mounts a tube support roller 40 on the piston and cylinder device 41 which in turn is supported on the quadrant 42. The quadrant 42 is adapted to be rotated so as to move the roller and piston device downwardly into the body of the wing to accommodate the motion of the carriage 32. The rotational motion is provided by the rack device 43 operated by the piston and cylinder device 44.

The drive for moving the carriage 32 back and forth on the wing is provided by prestressed continuous steel bands.

The bands for moving the carriage to the right to exert a pulling force are indicated at 49 and 50 (FIGURE 2). Since they are identically mounted, only band 49 will be described. The band 49 is secured to the carriage 32 by pin 51 and thence it goes over the pulley 52 rotatably mounted on the standard 53 fixed to the wing 4. The band then goes down over another pulley 54 also rotatably mounted on the wing 4. The band then winds over a pulley 55 rotatably mounted on a motor 56. The band then goes along the bottom of the wing where it is tied in by pin 60.

The motor 56 is a double-acting piston and cylinder device with one end of the piston locked to the wing 4 and with the cylinder being reciprocal. The pulley 55 is secured to one end of the cylinder. The band 50 is similarly arranged and is moved by the motor 56.

The band drive for moving the carriage to the left or towards the head stock includes the bands 61 and 62. As indicated in FIGURE 1 the band 61 is pinned to the carriage at 63 and extends along the top of the wing to the pulley 64 which is rotatably mounted on the wing. The band then goes to a pulley 65 which is mounted on the other end of the cylinder of the motor 56. The band 61 thence goes to the pin 66 where it is fixed on the wing 4.

Referring to FIGURE 1, if the cylinder of the motor 56 is moved to the right the movement of the pulley 65 will cause the bands 61 and 62 to move in translation and hence move the carriage to the left toward the head stock. The bands 49- and 50 will be pulled along by the carriage 32. The fully extended position of the cylinder to the right is shown by the position of the roller 55 at 55a.

With the carriage all the Way to the left, the gripper head 33 is located as shown at 33a. In this position it is set to engage a tube extruding from the throat of the rollers and to exert a pulling force on the tube so as to continue the extrusion. The pulling force on the carriage is developed by the motor 56 as follows.

With the carriage 32 adjacent the head stock the cylinder of the motor 56 will be all the way to the right. The bands 49 and 50 will extend from the pulleys 52 across the top of the bed to the carriage. If the motor 56 is energized to move its cylinder to the left, the pulley 55 will exert a force on the band and cause the same to move in translation and impose a pulling force on the carriage, i.e., move the carriage to the right.

With reference to FIGURE 1, it is pointed out that the force exerted by the bands 49 and 50 at the respective points of contact with the carriage 32 lie substantially in a plane which contains the axis A. Furthermore it is to be noted that the head 33 is preferably of a construction so that the gripping forces exerted on the end of the tube are concentric with the axis A. This concentricity and location of the pulling force properly biases the blank as it is pulled through the roller throat to enhance accurate concentricity and dimensions in wall thickness.

In connection with the above machine it is pointed out that we believe it is unnecessary to comment on the various structural details including the various hydraulic and electrical circuits and components which cause the machine to function as desired. Such components and circuits are of conventional design and are Well understood by those skilled in the art. Further, as will be apparent from the description below, the methods of the invention can be practiced on machines which entail quite different structural elements than the machine noted above. The manner in which the apparatus described above is manipulated to perform the methods of the invention will be described below.

In carrying out the methods of the invention a tubular blank is formed by conventional Ways; for example, by Wrapping and welding, spiral Welding, or by the use of a conventional tube mill.

The tubular blank is then loaded in them achine. This is done by rotating the tail stock 11 so that the mandrel assumes the position indicated by 17b in FIGURE 2. In the loading operation conventional handling equipment is used to support the mandrel in the outboard position and to support the tube while the same is inserted over the mandrel head. The tail stock is then rotated back to the position shown in FIGURES l and 2 and the left hand end of the tube is pushed firmly up against the support 23. The piston and cylinder devices 26 and 27 are actuated to grip and support the tubular blank.

The mandrel feed 12 is then actuated so as to move the mandrel and tube feed mechanism 13 to the right until the mandrell moves into the throat of the rollers as indicated at 17a in FIGURE 1. The right hand end of the tube is now spaced slightly to the left of the throat of the rollers.

At this juncture the blank feed cylinders are operated to move the blank to the right into the throat of the rollers. The rollers then work the wall of the blank and cause the same to extrude away from the throat of the rollers and from the mandrel in a direction toward the gripping head 33. The rate of extrusion of the tube away from the throat of the rollers is then measured. This can be done by conventional optical, hydraulic, or mechanical means. In the present instance a hydraulic-mechano arrangement is used and this comprises essentially a rod 70, which is contacted by the tube and thereby moves at the same rate. The motion of the rod is detected by the device 71. After the rate of extrusion is determined, the information is used to make the motor 56 operate to cause the carriage 32 to move at the extrusion rate. The carriage gets up to speed in a matter of seconds, and after this speed is attained the grippers (not shown) on the head 33 are actuated so that the extruding end of the tube is firmly engaged. Since the carriage is now moving, the tube is pulled toward the right.

It is to be observed that after the gripper begins to pull the blank through the roller throat the blank feed mechanism 13 is stopped and the left hand end of the blank pulls away from the support 23.

When the blank is completely pulled through the rollers the carriage 32 is stopped and the gripper head released and the carriage moved slightly further to the right. The tube and the carriage then assume the positions shown in FIGURE 1. The tube is now ready to be removed from the machine.

In connection with the practicing of the method of the invention it is pointed out that the transition from exerting a pushing force on the tube to the exerting of inside diameter and concentricity characteristics are of critical significance the indentation is of no consequence except from the standpoint of appearance.

Preferably the carriage is moved at the measured extrusion rate until all of the blank has been pulled through the throat of the rollers. It is pointed out, however, that it is not essential to maintain this rate so long as any change in rate does not effect a transient which could cause a groove or indentation or other impenfection of the tube surface.

In connection with the foregoing it is to be observed that other machine embodiments for practicing the invention may include carriage drive mechanisms of a more conventional type or less sophisticated type; for example, where the carriage mounts a hydraulic motor operating a nut connected with a screw on the wing.

With this type of machine the measuring and control equipment of the machine described above is eliminated. The extrusion rate of the blank is calculated or determined empirically and drive means for the pulling carriage preset to move the carriage at the desired rate. The gripping head grips the extruding tube just prior to enenergizing of the carriage drive.

With such arrangements it is preferable to include a yielding connection between the carriage and the gripping device. The yielding connection serves the important function of allowing the carriage to come up to the desired rate without a substantial backload being exerted on the tube. The yielding connection can take the form of a double acting piston and cylinder means with the piston connected to the tube gripper and the cylinder to the carriage together with valving operable to permit the flow of fluid between chambers to provide for the yielding and to stop the flow and maintain a hydraulic lock as the carriage gets up to speed and provide for trans- [fer of load between the gripper and the carriage for the pulling function.

Before closing it is pointed out that the invention is practiced under circumstances where the blank is under tension during the greater part of the working operation. In such instances the support 23 takes the form of a gripper and the tail stock 11 is mounted for movement along the wing. The power drive for the tail stock is controlled so that the rate of movement of the tail stock 11 and the carriage 32 are coordinated to provide for the desired tension.

We claim:

1. In a method of making a tube without end loss:

providing a tubular blank and a mandrel to support the blank in the throat of a plurality of rollers for the rollers to work the wall of the blank, the rollers and the blank being relatively rotatable in a direction around the periphery of the blank and the rollers and mandrel being fixed in a direction along the blank axis during the working operation; causing said peripheral relative rotation of the rollers and blank while maintaining said. fixed relation of rollers and mandrel;

exerting a pushing force on the blank to axially move the blank into the throat of the rollers to be worked thereby and continuing said axial movement and said working to cause the blank to extrude away from the throat of the rollers and from the mandrel; and

thence exerting a pulling force on the extruding portion of the blank and continuing; said working to cause said blank to continue to extrude away from the throat of the rollers and from the mandrel.

2. In a method of making a tube without end loss:

providing a tubular blank and a mandrel to support the blank in the throat of a plurality of rollers for the rollers to work the wall of the blank, the rollers and the blank being relatively rotatable in a direction around the periphery of the blank and the rollers and mandrel being fixed in a direction along the blank axis during the working operation;

causing said peripheral relative motion of the rollers and blank while maintaining said fixed relation of the rollers and mandrel;

exerting a pushing force on the blank to axially move the blank into the throat of the rollers to be worked thereby and continuing said axial movement and said working to cause the blank to extrude away from the throat of the rollers and from the mandrel;

thence without changing the rate of extrusion exerting a pulling force on the extruding portion of the blank and continuing said working to cause said blank to continue to extrude away from the throat of the rollers and [from the mandrel; and

continuing to exert said pulling force to cause said blank to continue said extrusion.

3. In a method of making a tube without end loss:

axially moving a tubular blank into the throat of a plurality of reducing rollers, the rollers working the blank and causing the same to extrude away from the throat of the rollers, and while the blank is being moved and is extruding, continuing said working and exerting a pulling force on the extruding portion to maintain the rate of said extrusion.

4. A method in accordance with claim 3 wherein a pulling force is maintained until the full length of the blank is extruded.

5. In a method of making a tube without end loss:

providing a tubular blank and a mandrel to support the blank in the throat of a plurality of rollers for the rollers to work the wall of the blank, the rollers and the blank being relatively rotatable in a direction around the periphery of the blank and the rollers and mandrel being fixed in a direction along the blank axis during the working operation;

causing said peripheral relative rotation of the rollers and blank while maintaining said fixed relation of rollers and mandrel;

exerting a pushing force on the blank to axially move the blank into the throat of the rollers to be Worked thereby and continuing said axial movement to cause the blank to extrude away from the throat of the rollers and from the mandrel;

measuring the rate of said extrusion;

causing a mean-s for exerting a pulling :force on the extruding portion of the blank to move axially at said measured rate of extrusion; and

thence causing said means to grip the extruding portion and exert the pulling force and continuing said Working to cause the blank to continue to extrude away from the throat of the rollers and from the mandrel.

6. A method in accordance with claim 5 wherein said pulling force is continued at said measured rate of extrusion.

References Cited UNITED STATES PATENTS CHARLES W. LANHAM, Primary Examiner.

E. SUTTON, Assistant Examiner.

US. Cl. X.R. 

